JP-A-2010-229885 describes a cogeneration system with the aim of efficiently using energy generated by combusting fuel.
In the cogeneration system, a generator is driven by a rotation power (mechanical energy) of an engine in which fuel is combusted, and outputs electrical energy. Further, water is heated by waste heat (heat energy) of the combustion, and the heated water is supplied from a hot water supplier, so that the energy obtained by the combustion is efficiently used.
However, the cogeneration system merely uses a part of the energy obtained by the combustion, that is, the potential energy of fuel is not sufficiently used.
For example, fuel before being supplied to the engine is not taken into consideration in the above system. The potential energy of the fuel before being supplied to the engine is not efficiently used.
Furthermore, gas exhausted after the combustion is not taken into consideration in the above system. The efficiency of the cogeneration system becomes low when the engine is activated with low operation efficiency to restrict air pollutant contained in the exhaust gas from being emitted to atmospheric air.
Heat energy is obtained when chemical reaction is generated between fuel and oxygen. However, the potential energy of fuel means not only the amount of heat theoretically generated by the fuel combustion but also internal energy of fuel before the combustion.